The present invention relates to the control of coil commutation in d.c. motors.
Known electronically commutated D.C. motors are provided with several shaft position sensors, for example Hall elements, which are each associated with a set of coils. The sensors are arranged in a set spatial pattern related to the positions of the coils. Signals are generated in the sensors, for example by the rotation of a rotor having multipolar permanent magnets, by means of which the instantaneous rotor angular position is sensed. Each respective coil commutation is triggered by these signals.
In addition, such motors require a rotation speed signal generator supplying information, i.e. signals proportional to the motor rpm.
Both kinds of information are required in order to provide motor control by means of electronic circuits.
Motors are also known in which motor control is based on shaft position sensing by means of a light barrier cooperating with a plurality of bar codes distributed around the rotor in a set relationship with the commutatable coils.